Rail systems are used for removably mounting accessories such as optical aiming devices on rifles. Such rails may be integrated with forearms or handguard elements that surround the barrel on firearms, such as the M4/AR15 configuration.
Integrated rails provide a solid and secure mounting location. However, integrated systems must have several rails of substantial length, to be able to accommodate all possible user accessory configurations. This undesirably increases the weight of the system.
Other systems have detachable rails that allow the user to install rails only where they are needed, and only of the length needed. While this decreases weight (and the discomfort and other disadvantages) of having needless rails where the hand is to grip, it suffers from other disadvantages. First, such systems may be difficult or complex to install. Second, they may require custom modification of parts, such as drilling and tapping holes where needed. Third, the attachment locations may be in limited locations due to the need to relocate fasteners such as threaded inserts (or may increase cost and weight by using an excessive number of fasteners).
A further significant disadvantage of systems having modular rails that may be mounted in various locations on the forearm or handguard of a rifle stock is the susceptibility to loosening. If the mount for a rifle scope becomes loose, this can cause significant aiming errors. The user may not notice the loosening or misalignment until after taking a shot that misses or strikes an unintended target.
Therefore, a need exists for a new and improved firearm that can be used to attach rails to a forend tube in such a manner that the rails do not change position over time. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the firearm with keyhole-shaped rail mounting points according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of attaching rails to a forend tube in such a manner that the rails do not change position over time.
An example of an approach to attaching an object to a surface using a keyhole slot is found on an adjustable slide board, which is from a field that is not analogous to the current invention. The slide board features two sets of longitudinally aligned keyhole slots. Bumpers are attached to the upper surface of the slide board by inverted T-nuts inserted into the keyhole slots and thumbscrews passed through bores in either end of the bumpers and threaded into the T-nuts. The underside of the slide board includes recesses at the narrow end of each keyhole slot that receive the heads of the T-nuts to secure the T-nuts within the keyhole slots when the thumbscrews are tightened. The bumpers are positioned laterally across the width of the upper surface of the slide board. The two sets of keyhole slots are offset so that the bumpers are attached at an angle to the sides of the slide board rather than perpendicularly.